Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Hint. Curl your right-hand fingers the way the current actually flows (clockwise, viewed from above) and see which way your thumb points.
Step 1 — Apply the right-hand rule to the loop. Curling the fingers of the right hand in the clockwise direction (as viewed from above the table, matching the current) points the thumb downward, into the table.
Step 2 — State the field inside the loop. The magnetic field inside the loop (and along its axis) therefore points vertically downward, into the plane of the table.
Step 3 — State the field outside the loop. Since field lines form closed loops, they curve around outside the loop and point in the opposite sense there — vertically upward, completing the loop back through the top.
✦ Answer: Inside the loop, the field points downward (into the table); outside the loop, the field lines curve around and point upward.
Where students slip. Giving the same direction for both inside and outside the loop — field lines form closed loops, so the direction outside is necessarily opposite to the direction inside, just as with a bar magnet.
